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Fox infanticide

(1) Fox infanticide - what is it?

It has been estimated that around 25% of mammals world-wide engage in infanticide, that is, adults will sometimes kill dependent youngsters of the same species, both their own youngsters and the young of others. And shocking as it may seem to most animal lovers, red foxes living in the UK countryside are included in this percentage.

Tiny, helpless fox cubs are easy prey for a passing, aggressive adult fox
Tiny, helpless fox cubs are easy prey for a passing, aggressive adult fox

It is often assumed that dog foxes - overly aggressive males - are predominantly involved in infanticide, but vixens, too, will sometimes kill cubs. However, given the animals' largely nocturnal habits and secretive nature, especially in the days immediately following births when the newborns and, to a large extent, the vixen stay underground, just how frequently this happens in the wild is not really known with any degree of certainty, nor are many of the precise circumstances.

It has been said, however, that in the first weeks of life, as many as 20% of cubs die underground, often as a result of squabbles with siblings; their tiny, lifeless bodies consumed by surviving brothers and sisters. Maybe the unfortunates were inherently weak - the runts of the litter - and destined for a short life; or maybe they were simply unlucky, always at the end of the queue when trying to suckle.

(2) Why do foxes sometimes kill fox cubs?

Quite apart from early deaths underground, a number of theories have been put forward to explain fox infanticide.

For example:

  • What could be described as aberrant behaviour in 'rogue' foxes might simply be as a result of a genetic pre-disposition towards infanticide, carried out for no obvious reason.
  • Undue stress, whether caused by on-going interference from more dominant local foxes or other factors, has been linked to both accidental and deliberate infanticide - a captive vixen on one occasion, for example, was seen to become very nervous, to seemingly panic and repeatedly, roughly carry her cubs in her mouth around the vicinity of the den, leading to their eventual, largely accidental death.
  • Foxes are hugely effective predators that survive by killing and eating other creatures, and so it may simply be that fox cubs provide a defenceless, easy to catch, tasty meal - certainly adult foxes have been seen to catch, kill and eat fox cubs.

And finally, two further possible drivers of infanticide have been proposed, both of which require a not unreasonable belief that foxes are incredibly intelligent animals and also incredibly devious!

  • Adult, dominant foxes may sometimes kill the cubs of other, often subordinate, foxes so as to:
    a) Reduce the competition for food, both whilst the cubs are dependent upon adults and after the cubs have started to fend for themselves.
    b) Encourage the bereaved vixen to devote her energies to feeding the cubs of the infanticidal fox.

Examples of fox infanticide

(3) Fox infanticide - a compilation video

The accompanying video is a compilation of clips from the foxes' den shown here - Fox cubs playing and 'play' fighting - which is the same den subsequently included on this page. It covers the hours of darkness on the 25th, 28th, 29th and 30th April, 2021.

Unfortunately, though, it is not possible to draw definitive infanticide conclusions from what is seen in this first video, but it does appear as though cubs were being carried by the vixen and they do seem to be lifeless.

(4) Fox infanticide video - commentary (continued)

Moreover, conclusions can't even be deduced from the number of live cubs seen, as the original litter size was not known nor was it known whether the cubs seen above ground at any one time were the only cubs present, particularly as activity at the other den entrance(s) was not monitored.

And further illustrating the difficulty of studying this sort of behaviour in the wild, the relationship between the vixen and carried cubs - if that's what they were - is equally unknown and so are the circumstances associated with each event.

Were they her cubs, for example, or were they cubs from another nearby den? If they were dead, did she kill them, did another fox kill them or did their deaths arise from natural causes? And if she killed them, why was this, has she done it before and would she be likely to do it again?

Definitive answers are hard to come by. Indeed, there is so much to learn, so much to try to understand, and all in the UK countryside without the need to ever travel to far-flung wild places.

A further example of fox infanticide - a dog fox carries away a pitiful, squealing, helpless cub and returns again and again, looking for more

The presence of an extremely aggressive, what was assumed to be a dog fox, may go some way towards explaining the actions of the vixen shown above. This interloper was first seen at the den at 04.00 hrs on the first of May, although a really strong foxy aroma was noticed nearby, for the only time, a couple of days earlier.

The dog fox was seen to explore the area of the den before on the following evening it seized and carried away a helpless cub - this doesn't make pleasant viewing. Further videos show the dog fox returning to the den, looking for more cubs to take, whilst at least a single cub remained present before the den was abandoned.

(The videos included below follow on from earlier videos showing the foxes den on the 29th and 30th April which confirm that at least three live cubs were present during the early hours of 29th April and at least one live cub was present during the evening of 30th April).

(5) In the early hours of 1st May, an interloper - presumably a dog fox - arrived at the den and prowled around (2 minutes 56 seconds video)

The vixen hadn't been seen since the previous evening when she carried a cub away from the den at 22.29 hrs, leaving behind at least one other cub that was last seen disappearing into the den at 23.01 hrs.

(It's probably reasonable to assume that the cub was still down there, but well away from the entrances).

Anyway, early that morning, at 04.00 hrs, an interloper, presumably a dog fox, arrived at the den and ominously prowled around. It repeatedly sniffed at both visible entrances and, in fact, briefly disappeared down both entrances on a number of occasions. It didn't find what it was looking for, however, and after 10 minutes, moved away.

The vixen returned with food for the cub(s) at 04.31 hrs, just 21 minutes after the interloper departed, and took the meal underground. She was not seen again that night.

(6) During the evening of 1st May, the dog fox returned and captured a cub (21 seconds video)

At 20.41 hrs it was still very light, the bluebells were in full bloom and all was well with the world. Or was it?

The dog fox arrived again and what followed was brief and extremely brutal. The dog fox's luck was in as a cub was close to the den entrance, but needless-to-say, the cub's luck had run out.

It is still too upsetting to describe what followed but it can be viewed in the video.

(7) Later in the evening of 1st May, the dog fox returned again, looking for more (1 minute 58 seconds video)

Not satisfied with taking one cub, the dog fox returned at 21.17 hrs, a mere 36 minutes after its first capture, on the lookout for another cub, another soft target to take who knows where. Thankfully, it departed empty-handed although judging by its rapid exit from the den, there was something in there that was willing to put up at least a bit of a fight.

What happened to the cub taken earlier in the evening was unknown, but its fate was probably extremely unpleasant.

The vixen was briefly seen at 22.41 hrs but did not go underground, whilst the predatory dog fox re-appeared again at 23.48 hrs but only gave the den entrance a rather cursory inspection, as shown below.

(8) In the early hours of 2nd May, the vixen returned four times and a single cub peeped out of the den - hooray! (2 minutes 16 seconds video)

Later that same night, in the early hours of the 2nd May, at 00.28 hrs, the vixen re-appeared, the first of four brief visits, all shown in the video below.

She looked lost, in a daze, unable to comprehend what had happened; and the single cub likewise, only momentarily glimpsed at the den entrance during the second visit, too afraid to venture out for fear of the potential consequences.

No food at all was seen to be brought back for the cub. The vixen seemed to have lost the will to continue with family life.

(9) At dawn on 2nd May, the dog fox was again on the prowl (20 seconds video)

(10) The predatory dog fox was seen for the last time on 3rd May (1 minute 17 seconds video)

During its last recorded visit, the dog fox somehow carried with it an air of disappointment - seemingly there were no cubs left to take.

(The camera was not put out on the evening of 2nd May nor after 3rd May).

Find out lots more about foxes

Introduction and description - an introduction to the Red Fox (Vulpes vulpes)
The foxes den / foxes earth - all about foxes' dens, and how to tell a foxes' den from a badgers' sett and rabbit burrow
Fox cub behaviour - a look in detail at the antics of fox cubs at the den
Fox cubs playing and 'play' fighting - a series of videos that include fox cubs playing and 'play' fighting at a den deep in the woods
Fox infanticide - an exploration of fox infanticide, the phenomenon of adult foxes killing fox cubs
Fox field signs, tracks and trails - a review of the signs that tell that a fox has passed by
Fox numbers - an examination of fox numbers nationally and more specifically in the New Forest
Fox watching - advice about watching country foxes without causing disturbance

References:
Collins Field Guide to the Mammals of Britain and Europe: David Macdonald and Priscilla Barrett
Town fox, Country fox: Brian Vesey-Fitzgerald
Animals Tracks, Trails and Signs: RW Brown, MJ Lawrence, J Pope
Collins Guide to Animal Tracks and Signs: Preben Bang and Preben Dahlstrom
Fauna Britannica: Stefan Buczacki
Running with the Fox: David Macdonald
Fox: Martin Wallen
Wild Fox: Roger Burrows
The Diary of Colonel Peter Hawker
Thirty-five Years in the New Forest: Gerald Lascelles
BBC Wildlife on-line edition
The Fox Website
Game and Wildlife Conservation Trust
Wildlife online - fox infanticide


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Content produced by Andrew Walmsley
Content produced by Andrew Walmsley